Infectious bursal disease (IBD) has previously been identified as a significant economic drain in the poultry industry. This disease, which strikes chiefly at the chicken industry, is caused by virulent field viruses which cause a highly contagious, immunosupprive disease condition. This condition, of course, exacerbates other infections in the chicken population. The disease is noted for its impact on young chickens, and is characterized by lesions in the lymphoidal follicles of the bursa of Fabricius.
In U.S. patent application Ser. No. 07/061,083, filed June 12, 1987, the inventor herein, and others, reported the development of two monoclonal antibodies sensitive to, and capable of neutralizing, all known viruses identified as inducing IBD. The entire disclosure of that application is incorporated herein by reference. Indeed, that application, which is still pending, addresses the monoclonal antibodies, particularly those identified as R63 and B69, expressed by hybridomal cell lines deposited in June, 1988 at the ATCC in Rockville, Md., U.S.A. under ATCC HB-9437 and HB-9490, which continue to prove their value as neutralizing monoclonal antibodies, comprising a passive vaccine against known strains of viruses inducing IBD.
Nonetheless, recent history in the poultry industry, particularly that along the eastern coast of the United States, reflects an increasingly large number of reports of outbreaks of infectious bursal disease, which are not fully prevented by any of the known vaccines, including those prepared from the monoclonal antibodies discussed above. Due to the severe economic strain placed on the poultry industry by these uncontrolled outbreaks, a significant degree of investigation of the cause of the outbreaks, and the reason for the failure of known vaccines to prevent such outbreaks, has been undertaken. No fault has been detected in the preparation of the vaccines, or their administration. Nonetheless, unchecked outbreaks continue to occur.
Accordingly, it remains a persistent problem of the prior art to determine the cause of these outbreaks of infectious bursal disease which are resistant to any of the known vaccines, and determine a method of preventing further such outbreaks.